Improved apparatus for making measurements in a well



pril 16, 1957 B. F. WILEY IMPROVED APPARATUS FOR MAKING MEASUREMENTS IN A WELL Filed Dec. 29, 1952 35mm HUM 3 Sheets-Sheet 1 INVENTOR.

Brucefi Wiley W J W7 ATTORNEYS A ril 16, 1957 B. F. WILEY 2,733,662

IMPROVED APPARATUS FOR MAKING MEASUREMENTS IN A WELL Filed Dec. 29, 1952 s Sheets-Sheet 2 G 2400 I I i I I C QSING JOINTS DEPTH- FEET WARMER IN V EN T 0R.

Brawl. Wiley A TTO RNEYS April 16, 1957 s. F. WlLEY 2,788,662

IMPROVED APPARATUS FOR MAKING MEASUREMENTS IN A WELL Filed Dec. 29, 1952 s Shets-Sheet a 63 62 RECORDER -IIlI I W/ H f gg K F/G. 5

INVENTOR. B BpuceEW lq A TTORNEYS United States Patent IMPROVED APPARATUS FOR MAKING MEASUREMENTS IN A WELL Bruce F. Wiley, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application December 29, 1952, Serial No. 328,295

12 Claims. (Cl. 73-151) This invention relates to an improved apparatus for making measurements in a well. In a more specific aspect, it relates to an improved apparatus for making differential temperature measurements in a well. In another specific aspect it relates to an apparatus for locating casing joints in a well.

In well bores in the earth, such as in oil wells, an increase in temperature is observed proceeding downwardly through the bore hole. In typical wells, the temperature gradient is of the order of 001 F. per foot.

Priorto my invention an apparatus has been devised for determining temperature conditions in a well comprising two pairs of coils, at opposite ends of a tool adapted to be lowered into a well bore, connected so that each pair of coils define the opposite arms of a-Wheatstone bridge. A current source is connected to one pair of opposite corners of the bridge and an indicator is connected to the other pair of opposite corners. A temperature differential is indicated by a difference in resistance of the coils resulting in unbalance of the bridge circuit. The position of the apparatus in the well is determined and recorded by the amount of cable payed out at the surface. This apparatus is described and claimed in copending application Serial No. 296,453, filed June 30, 1952, by Raymond G. Piety.

In the improved device of this invention, the two coils defining opposite arms of a Wheatstone bridge are wound upon a thin metal spool. The spool can be made of any metal but is conveniently made of brass and is preferably approximately 0.015 inch thick. The spool carrying the two coils is then covered with a thin metal sleeve, usually of the same metal and of the same thickness. The sleeve is sealed to the spool, for example by soldering, so as to hermetically seal the two coils in the resulting cylindrical container. The cylinder surrounds a recessed portion of the tool adjacent one end of the tool and is secured to the tool by several pipe supports so that there is an annular space between the cylinder and the tool. The leads from the coils extend through one of these support pipes into the interior of the tool and are carried from there to the surface by an insulated cable. Each pair of coils defining opposite arms of a Wheatstone bridge are confined in such cylinder one of which is positioned, as described, adjacent each end of the tool.

As the improved device is lowered into a well bore, the fluid in the well flows around the outside and inside of the cylinder housing the pairs of coils and as a result of the increased contact surface the sensitivity of the device is greatly increased by the improvement in the device.

This improved device has shown greater sensitivity to anomalies in the normal temperature gradient in well bores. In addition, this improved device indicates an anomaly to exist at each coupling of the pipe in the bore hole.

This phenomenon, indicated as a temperature anomaly is due to a magnetic effect. The electrical resistance of the coil is affected by changes in the magnetic field of the pipe. Each coupling in the pipe causes an anomaly in 2,788,662 Patented Apr. 16, 1957 the magnetic field of the pipe and these anomalies are indicated as abrupt surges in temperature since the instrument is calibrated to changes in temperature.

The two pairs of coils, each of which define opposite arms of a Wheatstone bridge, determine the temperature gradient in a well by the temperature difference between two spaced pairs of coils by means of the difference in electrical resistance in these pairs of coils, which causes an unbalance of the bridge circuit. Thus, differences in temperature are determined by this instrument as differences in the resistance of the coils to the electrical potential applied. Magnetic forces also effect the resistance of such elements, particularly if the coils are made of magnetic material. Thus, if the coils come into contact with magnetic forces which affect their electrical resistance, the presence of such magnetic forces will be recorded by the instrument and, since the instrument is calibrated to record in terms of temperature, the presence of such magnetic forces will be recorded as temperature changes.

It is common knowledge among those skilled in the art that a string of steel casing or steel drill pipe in a well will be magnetic. This is true, because, in placing a string of casing in a well, the casing will be subjected to jarring and to vibration While in the field of the earths magnetic force to the extent that the casing will become magnetized. The casing couplings apparently fail to connect the joints of casing into one magnetized bar, but instead, into a series of individual magnetized bars, or at least into a bar which lacks uniformity to the extent that there is a distinct magnetic field at each casing joint.

The effect is more pronounced when nickel or other strongly magnetic metal wire is used in the coils which define the arms of the Wheatstone bridge, however, satisfactory results are produced when copper wire is used.

The aspects of the invention will be obtained by the following objects.

It is an object of this invention to provide an improved apparatus for determining temperature gradients, particularly in well bores. It is another object to provide an improved differential temperature sensitive device which is sensitive to a magnetic field. Still another object is to provide a device for locating casing joints in a cased well or tool joints in drill pipe.

Other objects will be apparent to one skilled in the art upon reading the following description of the invention taken in conjunction with the accompanying drawing.

Figure 1 is an elevation of an improved differential temperature determining tool showing the thermistor device of this invention in partial section.

Figure 2 is an enlarged view in section of the thermistor device.

Figure 3 is a schematic diagram of the electrical circuit employed in the device.

Figure 4 is a log of a well obtained with the device of Figure 1 of the drawing of this invention.

Figure 5 is a view of the uphole apparatus which can be used with the device of Figure 1.

In Figure 1 is shown an elongated tool 10, adapted to be lowered into a well by a means (not shown) secured to threaded end 11. Recessed portions 12 and 13 adjacent each end of the tool are surrounded by sleeves 14 and 15 which are secured to tool 10 by supports indicated at 16 and 17. The tool body is advantageously made 8f msetal and covered by a plastic coating as indicated Coils defining opposite arms of a Wheatstone bridge circuit are hermetically sealed in sleeves and are indicated at 19 and 20.

Figure 2 shows in some detail the construction of sleeve 15 of Figure 1. Coils 19 and 20 are wound upon spool 30 and cover 31 is secured to spool 30 by some means 32, for example by solder. Leads 19' and 20' extend from coils 19 and 20 throughsupport 17 to the interior of tool and thence to an indicating means or current source which can be at the surface of the well.

Sleeve 14, which also comprises a spool and cover, is constructed in a similar manner as sleeve and carries the remaining two opposite arms of a Wheatstone bridge. The wires forming the coils are insulated, for example, by a lacquer coating.

In Figure 3, electrical energy, preferably alternating current, is furnished from source 41 to opposite corners of a Wheatstone bridge indicated at 42 and 43. Leads from the remaining corners of the Wheatstone bridge are taken oif at 44 and 45 and can be passed through a transformer 46 to an indicating device 47. The indicating device can be any instrument for sensing the output voltage of the system. The source of energy 41 and the indicating device 47 are preferablylocated at the surface of the well while the remainder of the circuit constitutes down-hole equipment. It is within the scope of this invention, however, to maintain one opposite pair of arms of the Wheatstone bridge at the surface and utilize the other opposite pair of arms of the Wheatstone bridge as the coil to be used in the well.

Figure 4 shows a section of an actual log of a cased oil well, made with the device of Figure 1. Examination of this log demonstrates the application of the apparatus of this invention in locating couplings in a jointed pipe in a well. Pipe couplings are indicated by the horizontal deflections in the log. This method of locating pipe joints or couplings applies equally well in locating tool joints in a string of drilling tools in a well.

In Figure 5, I have shown the uphole apparatus associated with a cased oil well. In this figure, the upper end portion 60 of the casing is set in concrete 61 and is provided with a gate valve 62 to which is attached a short threaded nipple 63. The upper end 64 of the cable passes over a sheave 65 mounted at the top of a derrick 66, and thence downwardly along the sheave 67 of a depth feeler wheel assembly 68 to a hoist 69. Rotation of the sheave 67 produces intermittent actuation of a switch 70 or other electrical component which is transmitted to a recorder 71 by a lead 72 and a return ground connection. Such devices are well known and provide an indication of the depth to which the tool assembly is lowered by the cable upon the recorder chart. The hoist 69 is provided with slip rings, one of which is indicated at 73, so that electrical connections are made from the conductors within the cable to the recorder 71 in the manner illustrated in connection with Figure 3. The recorder unit can also include the current source indicated in Figure 3.

The location of couplings is essential in certain operations in drilling and in maintaining an oil or gas well. An example is in the case of stuck drill pipe in drilling a well. It is often necessary to cut the pipe above the point of seizure in order to recover as much of the pipe as possible. In such case it is necessary to locate the tool joints so as to avoid attempting to cut the pipe at a tool joint.

Reasonable variations and modifications are possible within the scope of the disclosure of the present invention, the essence of which is an improved differential temperature indicating device which is capable of detecting the location of pipe couplings in a well bore.

I claim:

1. In an apparatus for determining temperature conditions in a Well which comprises an elongated tool adapted to be lowered into a well and having a pair of coils disposed at a location adjacent each end of said tool, wherein the coils at each end of the tool define opposite arms of a Wheatstone bridge, the improvement which comprises a thin metallic spool open at each end, surrounding a circumferentially recessed portion of said tool adjacent each end of said tool, each of said spools being adapted to receive and support a pair of said coils, a pair of thermal resistive coils wound about each spool; a plurality of supporting members securing said spools to said tool and spacing said spools from said tool so as to provide an annular space between each of said spools and said tool; a thin metal cover member secured to each of said spools so as to hermetically seal the coils therein, leaving the annular space open; leads extending from one pair of said coils through the interior of a supporting member to the interior of said tool and thence to a source of alternating current; and leads extending from the other pair of said coils through the interior of a supporting member to the interior of said tool and thence to an indicating device.

2. An apparatus for simultaneously making temperature measurements and detecting the couplings in a metal pipe in a well which comprises an elongated tool adapted to be lowered into said metal pipe in said well and having a circumferentially recessed portion adjacent each end; a thin metallic spool surrounding each of said recessed portions of said tool and spaced from said tool; a plurality of support members securing each of said spools to said tool so as to provide an annular space between said spool and said tool; a pair of thermal resistive coils wound together upon each of said spools and connected in a Wheatstone bridge circuit such that the coils at each end of the tool define opposite arms ofsaid bridge; leads from one pair of coils extending through the interior of a supporting member to the interior of said tool and thence to a source of alternating current; leads from the other pair of coils extending through a support member into the interior of said tool and thence to an indicating device at the surface of said well; and a thin metal cover secured to said spool so as to hermetically seal said coils in a thin metal container while leaving the annular space open.

3. The apparatus of claim 2 wherein said tool body is covered with a coat of plastic material, the spools are made of brass and said coils are made of nickel wire.

4. In an apparatus for determining temperature conditions in a well wherein a pair of wires defining opposite arms of a Wheatstone bridge circuit are wound together so as to form a coil and supported upon a device adapted to be lowered into said well the improvement which comprises a thin metal spool surrounding -a recessed portion of said device and adapted to receive and support a pair of said wires forming a said coil; a thin metallic cover secured to said coil so as to hermetically seal said coil in a resulting spool-shaped container; at least one hollow support securing said spool to said device and spaced from said device so as to form an annular space between said spool and said device; and leads extending from said coils to an indicating device.

5. The apparatus of claim 1 wherein the thermal-resistive coils are constructed of magnetic wire.

6. The apparatus of claim 1 wherein the thermal-resistive coils are constructed of nickel wire.

7. The apparatus of claim 1 wherein the thermal-resistive coils are constructed of copper wire.

8. In an apparatus for determining temperature conditions in a well wherein a pair of wires defining opposite arms of a Wheatstone bridge circuit are wound together so as to form a coil and a pair of such coils are supported upon a tool adapted to be lowered into said well, the improvement comprising said tool having spaced circumferentially recessed portions; a spool member surrounding each recessed portion; a pair of said coils supported upon each of said spools around said recessed portions so as to provide an annular space between said tool and each coil; a cover hermetically sealing each of said coils; and leads extending from said coils to an indicating device.

9. Means for logging pipe joints in a'well comprising a device adapted to be lowered into said well and having a circumferentially recessed portion; a Wheatstone bridge network including a pair of wires defining opposite arms thereof wound together to form a coil, encircling said recessed portion and spaced from said device so as to form an annular space between said coil and said device; a voltage source connected to said network; and an indicating device operatively connected to said network.

10. Means for logging pipe joints in a well comprising a device adapted to be lowered into said pipe and having a pair of spaced circumferentially recessed portions; a pair of thermal resistive coils encircling each recessed portion of and spaced from said device, each pair of coils defining opposite arms of a Wheatstone bridge circuit; a voltage source connected to said circuit; and an indicating device operatively connected to said circuit.

11. Well logging apparatus comprising a device adapted to be lowered into a well and having a circumferentially recessed portion; a thermal resistive coil encircling said recessed portion and spaced from said device so as to form an annular space between said coil and said device; a voltage source connected in a circuit with said coil; and means connected to said coil to measure the impedance thereof.

12. An improved apparatus for making measurements in a well comprising an elongated tool adapted to be lowered into a well and having a circumferentially recessed portion; a thin spool member, open at each end, surrounding said recessed portion; a thermal resistive coil wound about said spool member; a plurality of supporting members securing said spool to said tool and spacing said spool from said tool so as to provide an annular space between said spool and said tool; a thin cover member secured to said spool so as to hermetically seal the coil therein while leaving the annular space open; leads extending from said coil through the interior of a supporting member to the interior of said tool and thence to a circuit containing a voltage source; and means connected to said coil to measure the impedance thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,238,015 Doll Apr. 8, 1941 2,311,757 Jakosky Feb. 23, 1943 2,470,828 Millington May 24, 1949 2,517,455 Waters Aug. 1, 1950 2,540,588 Long Feb. 6, 1951 2,554,844 Swift May 29, 1951 2,676,489 Basham Apr. 27, 1954 

